root@ubuntu1204:~# apt-get update
Err http://security.ubuntu.com precise-security Release.gpg
  Temporary failure resolving 'security.ubuntu.com'
Err http://ca.archive.ubuntu.com precise Release.gpg
  Temporary failure resolving 'ca.archive.ubuntu.com'
Err http://ca.archive.ubuntu.com precise-updates Release.gpg
  Temporary failure resolving 'ca.archive.ubuntu.com'
Err http://ca.archive.ubuntu.com precise-backports Release.gpg
  Temporary failure resolving 'ca.archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://ca.archive.ubuntu.com/ubuntu/dists/precise/Release.gpg  Temporary failure resolving 'ca.archive.ubuntu.com'

W: Failed to fetch http://ca.archive.ubuntu.com/ubuntu/dists/precise-updates/Release.gpg  Temporary failure resolving 'ca.archive.ubuntu.com'

W: Failed to fetch http://ca.archive.ubuntu.com/ubuntu/dists/precise-backports/Release.gpg  Temporary failure resolving 'ca.archive.ubuntu.com'

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/precise-security/Release.gpg  Temporary failure resolving 'security.ubuntu.com'

W: Some index files failed to download. They have been ignored, or old ones used instead.
root@ubuntu1204:~#